The invention relates to a rotation joint, especially for medical instruments, with a proximal and a distal part that are coupled to one another by means of a gear work and can be adjusted in relation to one another between a non-deflected starting position and an angled end position, where the gear work is housed in an intermediate part situated between the proximal and the distal parts and all three parts have at least one hollow center channel.
Various constructions are known from medical technology which serve to alter the angle of deflection of the working parts of a medical instrument from the longitudinal axis of the housing. These known rotation joints often have the disadvantages that the change of the angle setting cannot be actuated remotely, that is, from a position distant from the actual rotation joint; or that the determined angle setting cannot be secured; and/or that the rotation joints have no hollow central channel for the purpose, for instance, of actuating the working parts on the distal end of the instrument by way of a cable pull.
A rotation joint of the aforementioned type is known, for instance, from U.S. Pat. No. 4,641,657. This familiar rotation joint has the disadvantage that the angle setting of the individual rotation joint parts to one another is changed by turning the intermediate part, so that remote operation of the rotation joint is impossible. In addition, the previously known construction has no means to secure the rotation joint in the deflected position.
On this basis, the aim of the invention is to perfect a rotation joint of the type cited at the outset in such a way that the rotation joint can be actuated from a position distant from it and that the selected angle setting of the rotation joint parts to one another can be secured.
This aim is fulfilled by the invention in that the proximal part consists of two tubes that are arranged coaxially inside one another and can rotate in opposite directions around their longitudinal axis, where at least the outer tube is connected with a handle on its proximal side.
By means of the handle connected with the outer tube of the proximal part, it is possible to displace the rotation joint by turning the outer tube without the necessity of directly displacing the intermediate part containing the gear work. In addition to the remote displacement of the rotation joint, the handle allows the rotation joint to be secured in the particular deflected position. An additional advantage of the inventive construction is that the rotation joint is very rigid because of the coaxial arrangement of the two tubes forming the intermediate part.
To ensure that the rotation joint can be rotated to the desired angle without any loss of rigidity, it is proposed in a further refinement of the invention that the terminal surfaces of the distal-side end of the proximal part and of the proximal-side end of the distal part, which surfaces are turned toward one another and, in the starting position, are adjoining the terminal surfaces of the intermediate part, are inclined toward one another at the same angle toward the longitudinal axis.
It is further proposed, through the invention, that the inner tube on the distal side is equipped with a gear wheel of the gear work and that a steering pin is mounted on the distal-side terminal end of the outer tube, where the steering pin engages into a corresponding recess of the intermediate part. Because of the invention""s design of the proximal part of the rotation joint, it is possible to change the angle setting of the rotation joint by turning either the inner tube or the outer tube independently of one another.
In a preferred embodiment of the invention, it is proposed that the gear work consists of at least two beveled wheels engaged with one another, where one beveled wheel is connected with the distal-side end of the inner tube and another beveled wheel with the proximal-side end of the distal part. The use of two beveled wheels engaged with one another makes it possible to diverge the proximal and the distal ends of the rotation joint, each by the same angle to the longitudinal axis.
To achieve an especially flat curvature between the proximal part and the distal part, another means of reducing the risk of crushing the actuation material conducted through the hollow central channel, it is proposed in a second embodiment of the invention that the two beveled wheels connected with the proximal and distal parts are connected with one another by way of a beveled wheel housed in the intermediate part. The intermediate piece in this variant is extended by the radius of the additional beveled wheel, which results in a greater radius of the curvature.
Finally, it is proposed with this invention that the maximum angle of diversion of the rotation joint of this design between the starting and end positions is determined by the formula 4xc3x97(90 degreesxe2x88x92alpha). For a maximum angle of diversion of 90 degrees, therefore, the value for alpha is 67.5 degrees and for a maximum angle of diversion of 180 degrees the value for alpha is 45 degrees.